What is the purpose of a "Y" valve in a marine toilet system?

The purpose of a "Y" valve in a marine toilet system is to allow waste disposal either into a holding tank or directly into the water. This versatility is crucial for boaters because it enables them to comply with environmental regulations that often require waste to be kept in a holding tank in designated areas or when near sensitive ecosystems. When it is permissible to dispose of waste directly into the water—usually when a certain distance from shore—the "Y" valve can be switched to facilitate that process, thereby providing boaters with flexibility in managing waste systems according to regulatory requirements and environmental best practices. This functionality helps ensure that waste is disposed of appropriately based on the boat's location, thereby reducing the risk of pollution in recreational waters.